The present invention refers to sound-insulating sandwich elements, more specifically to sound-insulating multilayered building or construction elements or components such as doors, partitions, walls or ceilings comprising an open-cell, semi-rigid foam core consisting of at least one core material, and comprising one or more than one hollow space or air gap located within the core, and comprising two outer facing layers.
More specifically the invention refers to sound-insulating sandwich elements, such as doors, partition elements, walls, ceilings, floors, bulkheads, fire doors, traps, lids, flaps, windows, compartment elements, or panels in new or existing buildings. The new sandwich elements are useful in buildings, in the construction industry, or other industries in order to improve the sound-insulation performance. Besides, the invention refers to sound-insulating elements excelling prior art elements in constructional simplicity, mechanical strength, and rigidity and to the use of such new, sound-insulating, multilayered sandwich elements in the construction or other industries for acoustically improving walls, partitions, ceilings, and other parts of the building, structure or machinery.
In the construction industry, it is well known to use panels as partition walls in order to subdivide the building area into seperate areas such as rooms and offices. Usuall, they consist of an insulating mineral fiber core and two outer facing layers encompassing the core and an air gap or hollow space. The insulating materials such as mineral fibers are arranged between the facing layers in such a manner so as to provide thermal and/or acoustic insulation.
It is also known to use multilayered sound-insulating sandwich elements, laminates or boards, containing mineral fibers as insulation material, as partition elements or compartment elements or panels to be fixed to walls or ceilings to the intention that sound and noise propagation and transmission and sound radiation are reduced. By applying sound-insulating elements to walls or ceilings or by using them as partition elements it is possible to upgrade residential buildings or office buildings improving their sound-insulation performance. Thus, older constructions can be adjusted to comply with modem often higher regulation standards. Noises from neighbors or external sources or emanating from inside the room can be reduced substantially.
However, a major disadvantage of such partitions or panels having mineral fiber cores is the lack of mechanical strength of such fibers. For that reason the facing layers must be secured, for example, by means of screws or frames, and supported by metal or timber studs. This requires an extensive manufacturing process.
In JA 0221 642, a noise insulating panel is disclosed in which a porous material, such as glass wool or foamed synthetic resin is stacked between facing layers formed by plywood, gypsum board, or an acryl plate in such a manner as to be out of contact with at least one surface material. According to the teaching of this specification, a frame must be used in order to stabilize or fix this condition. This frame is fitted to the above assembly to form a panel. This, of course, is a relatively intricate and hence expensive procedure. Furthermore, it is a well-known method extrapolated from conventional timber frame walls or panels.
DE 3710 057 discloses a multilayered acoustic insulation panel for internal walls which has air gaps between a layer of mineral wool and an outer chipboard facing layer. This insulation panel contains a main panel made of chipboard, which is spaced apart by ribs from a facing layer, or cover panel which is also made of chipboard. The inner surfaces of these two panels are covered with fiberboard which is held in place by glue. For attaining good sound-dampening performance the two fiberboards are different in weight. This multilayered panel consists of five layers, that is, two chipboard layers, each of which is glued to a fiber board, plus a mineral wool layer in the middle of the sandwich serving as acoustic insulation material. The mineral wool fills the space only partly in such a way that an air gap is provided for between the mineral wool and one of the fiberboards which is glued to the inner surface of the cover panel. The latter is secured by screws to the ribs. As can be seen from the description, the design of this multilayered panel is quite complicated. Its fabrication is therefore relatively expensive. The acoustic performance is achieved by increasing the mass rendering such panels difficult to transport and to install.
According to several proposals, organic plastics have been used instead of mineral fibers, such as, for example, the well-known open-cell polyurethane foam laminates. However, such laminates exhibit the disadvantage of being brittle and having a poor tensile strength (about 30 kPa).
In U.S. Pat. No. 4,317,503 a sound-insulating building element is disclosed which includes a plurality of parallel layer elements of which a first inner, thick element is constituted by a layer of mineral fibers or stiff plastic foam and contains a plurality of cavities. A second inner stiff element which is substantially pervious to air is connected to one main surface of the first inner element and an outer impervious element. The outer impervious element is arranged at a small distance from the second inner element in such a manner that substantially the entire outer element can oscillate freely in relation to the second inner element. A major disadvantage of this type of building element is the complex and costly manufacturing process of such multilayered structures.
Other known types of partitions are the multilayered structures including those having a foam or honeycomb core. The foam cores, however, although possessing suitable mechanical strength properties, are very poor as far as the sound-insulating properties are concerned. In order to overcome this problem, the foam core would have to be of an unacceptable thickness and weight.
Generally speaking, there are several known types of systems for increasing the sound-insulation performance of walls such as:
increasing the mass of the wall which is, of course, the most basic way of providing better sound-insulation (mass law);
using resilient panels or sandwich structures the components of which, that is facing layer or layers and core layer, vibrate without phase relation so that part of or most of the incident acoustic energy is converted into mechanical energy, which will be dissipated through internal friction and deformations (mass-spring-mass system).
The drawback of the increase of the mass of the wall or any similar structure following the mass law is that rather heavy and thick structures are required for good performance.
The drawback of common mass-spring-mass systems is that their resonant frequency will very often disturb the overall performance when it is wrongly positioned and too sharp.
Better results are obtained by using sound-insulating elements or panels as disclosed in WO 95/14136. Those multilayered insulating panels or elements comprise in a preferred embodiment (a) two outer facing layers, and (b) a soft synthetic core material which is a single, continuous, soft, synthetic foam core layer having cavities and being arranged in intimate contact with both outer layers through contact points in alternate patterns, thereby providing gaps between the core layer and the opposing outer layer.
What is actually disclosed in the specification, the drawings, the claims and the abstract of WO 95/14136 is the following:
a sandwich element comprising two facing layers, for example, gypsum boards, and a core material between the facing layers;
the core layer comprises an elastic, closed-cell polyethylene foam, or rigid, closed-cell polyurethane foam, or other closed-cell plastic foams, for example, based on polyvinyl chloride, or polystyrene;
the second facing layer can be a brick structure, thus referring indirectly to a wall, to which the core layer can be glued, for example, with mortar;
the core layer contains cavities in special geometrical arrangement; there are gaps between the core layer and the facing layers;
the gaps are confined between the core layer and the facing layers by contact points or areas which are arranged in an alternate pattern with respect to the opposing facings; and
empirical measures and theoretical considerations are applied for best results in the mass-spring-mass-system.
Panels as disclosed in WO 95/14136 possess both acoustic insulating properties and mechanical strength. While this art provides lighter and cheaper panels with good acoustic properties compared to previously known products, it was still highly desirable to provide room partition elements and sandwich elements such as doors, and partitions having both sound-insulating properties and good mechanical strength, which would be particularly useful for up-grading residential and office buildings and for designing partitions with improved sound-insulation performance. Also, there was a need for more economical methods for producing and installing such sound-insulating panels.
The previous European Patent Application 98 111 295.6-2303, is directed to a multilayered, sound-insulating panel comprising a facing layer, a plastic foam core layer attached thereto wherein the core layer material is a semi-rigid, cellular material having certain characteristics, a structure, to which the core layer is fixed at seperate contact points by means of strips, patches, dabs, or other geometrical protrusions (generally called xe2x80x9ccontact pointsxe2x80x9d) leaving gaps between the core layer and the structure, and, in case of long spans and/or thin facing layers, travel stops to keep the core layer at a certain distance from the structure.
The panels according to EP 98 111 295.6-2303 are useful in the construction and other industries for improving the sound-insulating properties of buildings and/or machinery.
Although these sandwich elements are in general suitable as partition elements their mechanical strength may not be sufficient due to the presence of the large gap between the facing and the core in application fields where strength and resistance are of particular importance to the applicability of a construction element, such as in the construction of doors or walls.
That need and other needs are met by the present invention. Thus, the present invention provides a multilayered, sound-insulating sandwich element comprising facing layers and a plastic foam core located between the facing layers and attached to the facing layers, the core presenting one or more than one cavities, which sound-insulating element is characterized in that:
the cavity/cavities is/are a gap/gaps which is/are positioned essentially parallel to the facings and is/are located within the core;
the core material is a semi-rigid, cellular material containing more than 50 percent, preferably more than 90 percent open cells;
and has a tensile strength of more than 50 kPa, preferably more than 90 kPa;
and has a compressive strength from 5 to 200 kPa, preferably from 15 to 80 kPa, at 10 percent deformation.